Historically, extraction and concentration of substances from test samples, such as environmental pollutants in water and drug related substances in blood serum, are carried out in either a separate extraction apparatus and a separate concentration apparatus, or in a combined extractor/concentrator apparatus.
As is well known in the art, extraction is conducted by passing a suitable solvent through a test sample in order for the solvent to combine with any subject substance that may be present within the sample. After the sample has been adequately exposed to the solvent, the substance carrying solvent is then transferred to a separate concentrator for distillation of the solvent thereby leaving behind a concentration of the substance being sought. If a combination extractor/concentrator apparatus is being used, a valve usually located along the extract connecting tube is closed after the sample has been adequately exposed to the solvent and the substance carrying solvent has passed to the concentrator. The concentration of the substance is then increased by distilling the solvent, thereby leaving behind a concentrated solution of the subject substance.
The particular apparatus used, regardless of whether a separate extractor and concentrator or a combination thereof is used, will also depend upon the relative densities of the solvent and the sample. This is because the solvent must be introduced to the sample from above or below the contained sample depending on the relative densities of the sample and the solvent being used, in order for the solvent to pass through the sample via gravitational forces. Therefore, care must be taken to introduce the proper amount of sample and solvent into the apparatus, so that the sample and the solvent can be processed accordingly. Additionally, the apparatus must also be designed to prevent the solvent and/or the sample from back flowing through the apparatus due to head pressures.
Representative prior art of a separate extractor for use with solvent that is of greater density than the sample and a separate concentrator are shown in FIGS. 1A and 1B respectively.
Representative prior art of a combined extractor/concentrator apparatus for use with a solvent that is of greater density than the sample is shown in FIG. 2.
Representative prior art of a combined extractor/concentrator apparatus for use with a solvent that is of lesser density than the sample is shown in FIG. 3.
Prior art apparatus typically use permanent connecting arms and connecting tubing, also referred to as cross over arms and siphon tubing, which serve to fluidly connect a portion of the apparatus to another portion of the apparatus. A shortcoming with such prior art connecting members is that they can be difficult to clean, especially if they are of a serpentine nature. Cleaning difficulties not only increases labor costs, but an improperly cleaned tubing increases the chances of contaminating samples that are to undergo processing with previously processed samples and/or solvent remaining within the tubing.
An additional shortcoming with prior art apparatus is the fragile, breakage prone nature of the apparatus due to the connecting arms and tubing being fused, or otherwise permanently attached, to the appropriate portions of the apparatus. Furthermore, repair of damaged tubing can be expensive and if the damaged tubing can not be repaired economically or promptly, the entire portion of the affected apparatus must be replaced.
Another shortcoming with prior art apparatus is a specifically designed apparatus must be used with solvents having a density greater than the sample to be processed. Conversely, a specifically designed apparatus must be used with solvents having a density lesser than the sample to be processed.